For nearly three decades, solar energy has been a future source of sustainable energy. Optimists still stand their ground but many analysts think that it will continue to be in this position for quite some time, incapable of surviving without subsidies.

That does not mean that solar energy market is not growing or technology is not advancing fast enough. A report two months ago by TechNavio, part of the market research firm Infinity Research, predicted a 15.3% annual growth for the industry in the next three years.

A McKinsey report published six months ago was even more optimistic, saying that solar cell cost will continue to drop 10% every year till 2020, by which time 400-600 gigawatt of capacity would have been added globally. Solar technologies also form an active area for research. A large number of new technologies are entering the market, thereby decreasing the dominance of silicon photovoltaics.

One of most promising is thin film: projects in India are using it heavily already and technology is rapidly advancing in this field. Also in the works are new solar thermal technologies, plasmonic solar and all-carbon solar cells, not to speak of new system designs and manufacturing techniques. The next decade could also see the emergence of artificial photosynthesis, the holy grail of solar energy research.

We describe a pick of some advances that seem promising.

Carbon Solar

Replacing silicon with carbon is a good way of making solar energy cheap and ubiquitous, but so far this feat has eluded scientists. Now researchers at Stanford University and Massachusetts Institute of Technology (MIT) demonstrate two different methods to make all-carbon solar cells.

The Stanford method could lead to cheap and flexible solar panels, while the MIT method could be combined with silicon technology to make more efficient solar cells.

3D Solar

Why should solar cells remain aloof in an increasingly 3D world? MIT researchers have demonstrated that stacking them in three dimensions can help produce 20 times more power per square foot than using flat panels.

This and other 3D designs could help solve one of the most serious drawbacks of solar electricity: requirement of a large surface area.

Â

Thin Film Flexible solar cells have a number of uses in daily life. Researchers at the University of California in Los Angeles have come up with a novel idea: make them flexible as well as transparent. In fact, their solar cells are transparent to visible light but absorb infra-red.

This means that you could coat anything - phones, wristwatches, cars - with this material and they continue generating electricity. Infra-red radiation is present everywhere. Even at night.

Cheaper Solar Cells

The process for making silicon wafers requires expensive equipment. Silicon -Valley-based Crystal Solar has now demonstrated a commercial process that skirts the wafer step, by making thin solar cells directly out of gas. This is supposed to cut by half the capital cost and energy use for manufacture. Expect a commercial launch by 2014.

Three months ago, IBM scientists demonstrated how a combination of copper, zinc, tin, and selenium (CZTS) could be used to make thin film solar cells of 11.1% efficiency. Their aim is to reach 20% efficiency with these earth-abundant materials, and replace the nowcommon CIGS solar cells. The potential is 500 gigawatts per year.